This invention relates generally to network security, and more particularly, to a system for providing key management between a server and a client, e.g., in a telephony or an IP telephony network.
In networks that are based on a client/server configuration, there is a need to establish a secure channel between the server and the clients. In addition, in networks that utilize a third party to certify a trust relationship, there is a need to provide an efficient mechanism that allows a key management message to be initiated by the server. In such networks that utilize a trusted third party for the server and client, the client can typically request an encrypted authentication token from the trusted third party that can be used to initiate key management with the specified server; however, the server will typically initiate the key management session directly with the client. It is less preferable for the server to obtain from the trusted third party encrypted authentication tokens for each of the clients. Such an approach would add overhead to a server, requiring it to maintain cryptographic state for each of the clients. If such a server were to fail, a backup server would be required to undergo a recovery procedure in which it has to obtain new authentication tokens for each of the clients. The clients need to be initialized during their provisioning phase to allow them to successfully authenticate to a trusted third party and obtain the encrypted authentication tokens. One proposed method for client initialization is disclosed in PCT Application No. PCT/US00/09318 entitled “BUILT-IN MANUFACTURER'S CERTIFICATES FOR A CABLE TELEPHONY ADAPTER TO PROVIDE DEVICE AND SERVICE CERTIFICATION.” Nevertheless, a need exists to provide an efficient mechanism through which the server can initiate the key management session with the client, as opposed to a system in which only the client can initiate such a session.
One such client/server network is the client/server network that exists in IP telephony. In IP telephony systems, a cable telephony adapter (CTA) device can be used to allow a user to send and receive information in secure transactions over an IP telephony network. In typical operation, a series of signaling messages are exchanged that register the CTA device with the IP telephony network before a secure channel with another user can be established. Therefore, the CTA device needs to be authenticated by the IP telephony system. Otherwise, the process would be open to denial of service attacks—since some provisioning exchanges can be forged. In addition, it is desirable for the service provider to identify the CTA device—to make sure that only authorized devices are allowed in its IP Telephony network.